The whole-earth nature documentary space is quickly becoming crowded. We've got:
The Blue Planet, 2001
Deep Blue, 2003
Planet Earth, 2006
Earth, 2009
Nature's Great Events, 2009
Oceans, 2010
The last one on the list is from Disney. If you watch the trailer, the company is attempting to say, "Planet Earth? Ha! Disney was down with nature all along!" Pfft. A point in Disney's favor however is that Oceans is being done by Jacques Perrin, the man responsible for Microcosmos and Winged Migration. Points against: the film has cost $75 million so far (for a documentary!), the footage in the trailer looks like it was lifted directly from The Blue Planet and Planet Earth, and no David Attenborough narration.
Update: I added Earth to the list, also from Disney. Here's the trailer. BBC and Discovery are listed as partners so it's likely that the footage in the film is from Planet Earth. (thx, @gjdsalinger)
Update: Earth is indeed mostly material taken from Planet Earth. Disney helped bankroll the production in the first place.
Update: I added Deep Blue to the list as well, a feature-length version of The Blue Planet. (thx, @aknock)